Technical Abstract:
The objective of the study was to determine the effect of dietary boron supplementation on sperm production and semen quality estimates in mature boars. Twelve crossbred boars (Landrace x Large White x Duroc x Hampshire) that were 2.5 +/- 0.2 years of age and 215 +/- 5 kg were randomly assigned to receive 0, 9.3, or 92.6 ppm of boron per day for 8 weeks (n=4 per treatment). Supplemental boron was added to their basal diets and boars were fed 2.75 kg daily of a corn-soybean meal diet (14% crude protein) that exceeded all other nutritional requirements. Concentrations of boron in the whole semen and seminal plasma fractions of ejaculates collected at the end of 7 weeks were different among treatments (P<0.05). The highest and lowest levels were measured in boars receiving 92.6 ppm (708.7 and 692.0 ng/ml) and no supplemental boron (88.9 and 76.5 ng/mL), respectively, while concentrations in boars receiving 9.3 ppm (148.0 and 145.4 ng/mL) were in between the other two treatments. No effect of time or treatment on semen volume (P>0.70); total number of spermatozoa per ejaculate (P>0.82); or the proportion of spermatozoa exhibiting progressive forward motility (P>0.89) was observed. There was a tendency for a time by treatment interaction (P=0.09) for the proportion of spermatozoa with normal morphology. Normal morphology averaged 72.0% for control boars and did not change over time (P>0.89). In contrast, it tended to increase (P<0.10) from 74.7% and 76.1% during the first week of the study to 86.4% and 88.2% during week 8 in boars fed 9.3 and 92.6 ppm of boron, respectively. Average path, straight line, and curvilinear velocities of motile spermatozoa increased over time (P<0.05) in boars receiving supplemental boron, but remained constant (P>0.45) in control boars (treatment x time; P<0.05). In conclusion, supplemental dietary boron enhanced sperm velocity characteristics and possibly, normal morphology, without influencing other measures of sperm production and semen quality.